Friday, September 19, 2008

Aviation Green Prize Rules

Beginning on September 19, 2008 and ending on October 3, 2008, CAFE opens a 2 week comment period for all interested parties to examine and post suggested changes for the Aviation Green Prize Rules. A draft of the rules in .pdf format is available [here] and the rationale for these rules is available as a .pdf [here]. To participate, please first download and read the rules and rationale. Then you can post your comments on this site by clicking [here]. You will need a Google or OpenID account to post a comment. CAFE appreciates all input and suggestions for this great event.

28 comments:

Like the Progressive Automotive X Prize, the rules reward best speed among those achieving ≥ 100 MPGe. The MPG is based upon the relative market price of fuel/electricity. This fluctuates and is going to undergo major changes in the future. Small changes in market prices would cause big changes in MPG scores WITHOUT ANY TECHNOLOGIC ADVANCE in the vehicle. However, going faster demands an actual advance in technology or design. Therefore, once having achieved 100 MPGe, speed is the metric that should be rewarded.

Well, based on this past year's rules, we were planning to compete next year. BUT, while I can easily get 30-40 mpg at 100 mph, 100 mpg is still many years away. Even 50mpg isn't doable without going electric or hybrid, and our budget doesn't allow for that kind of R&D. Perhaps Michael is right: This competition has been tailored to Universities and Corporations with deep pockets, not the rest of us.

This is an ambitious set of requirements, but I believe it's necessary to stimulate a major advance. One of the disappointments in prior CAFE competitions has been how easy it was to win them by tuning up conventional existing systems and airplanes. I think there should be an exponential reward scale, so that if no one achieves the goal, competitors who come close to it or achieve a significant step-function advance over existing record performance receive enough money to induce them to continue their effort.

Rules seem to be overly restrictive. I remember Peter Diamandis of the X prize organization talking about how rules that are too restrictive can greatly reduce the available creative design space. Also, I know one group that wanted to bring an experimental aircraft for the handling qualities prize that now say they probably can not afford the registration fees.

Al major aciation advanes have been fostered by Challenges like this historic one. And Universities do Not have 'deep pockets'. Does not need much money, only brilliant ideas. The technology may be here, or almost is. Remember the 'impossible' requirements for the first Transatlantic? Or the first Round the World unrefueled non-stop powered flight. Was only ouple decades ago. Or the First Human-Powered Cross-Channel same recency? Or the First powered Aircraft Cross-Channel, by a revolutionary Monoplane, Bleriot. You guys been too used to Big Power speed? Only needed by Too late big timers :) Tony, a future LSA pilot, waiting on Advanced Pipstreleze :)

I fear the rules are too restrictive to inspire and attract much innovation. It's not likely that an innovative aircraft will meet every minimum entry requirement. Our own company was unable to compete previously because of our 57mph stall speed (low for a 200mph airplane). I think it would be better to loosely define the contest goals and give contestants as much slack as possible... it works at science fairs.

I believe the aggressive goals will prompt major advancements - this is very worthwhile.

I suggest that the equivalency between alternative energy sources is set not by economic cost but rather by equivalent energy. I suggest that 100 miles per gallon on the 200 mile course is defined by using the energy in two gallons of 100 low lead aviation gasoline. This quantity weighs about 12.04 pounds and has about 240,400 British Thermal Units (BTU) of energy. This energy is equivalent to 70.45 kilowatt-hours.

Hi Cafe Foundation, just a few comments, ive followed the competion the last 2 years, and am interested in competing next year(2009). i would like to see the competion be realistic though, for the cut off of prizes. 100mpg??lol...the pipistrel has been the best winner so far, but last year couldnt quite reach 30 mpg. when i attended the sunday open house this past summer, a young gal (docent) told me the cut off for next year would be 35 mpg for the green prize. To enter the competion takes a huge ammount of time, resources and money. only a few airplanes have entered the past 2 years, please keep the cut offs for the prizes attainable. Bump it up a little each year in each catagory. Also please post asap the competition dates and catagories with rules for next year. Anyone interested needs to start planning now. Always holding your organization in high regard, i worked in the tower at STS for many years, thanks michael radtke.

Any 100mpg aircraft will likely have a wingspan exceeding 44ft. I'm therefore concerned about the rule that requires the wingtips to remove or fold to a 44ft span for the purpose of fitting inside the CAFE hangar during weighing. I recommend a more suitable weigh location so that competitors are not burdened with this restriction...it's easier to move the scales than to modify wings. -David

It seems to me that there needs to be an alternative way to measure the MPGe for hybrid powered air vehicles.

I'll define hybrid here as a vehicle that uses electricity and some other type of fuel. There are basically 2 types of hybrids.

The first type, like a Toyota Prius, uses electric and internal combustion motors to do the required work (drive a wheel, turn a propeller, etc). Each motor is fueled independently. Batteries power the electric motors while gas, diesel, jet a, etc powers the conventional engine. The motors produce power independently but work together delivering the power so it can be used. The CAFÉ MPGe formula works fairly for this type of hybrid.

The second type of hybrid use batteries and an additional motor/fuel cell to recharge those batteries. This type of system is similar to what Chevy is doing with the Chevy Volt or what numerous auto makers are doing with fuel cell powered vehicles. An air vehicle that uses this arrangement would in essence be “charged” twice for the energy used to recharge the batteries (once when the fuel is consumed to recharge the batteries and then again when the batteries deliver the electricity to the motor).

This imposes a severe penalty on this type of vehicle. One possible solution would be to subtract the electricity produced by the fuel cell or generator from the total amount of electricity consumed.

If I’m looking at this incorrectly please forgive me, I majored in business, not engineering.

Please eliminate the 44 in cockpit requirement, 2 normal size people could fit in a with of 40 inches for a 2 hr/ 200 mile flight thanks., the plane i have to enter the competition is 40 in. maybe just eliminate the with requirement entirely

Dear CAFE and NASA,We believe that the rules are set high enough to be insteresting and we are already looking forward to see how the 2009 challenge will evolve. We are all very excited to prepare an aircraft to fulfill the goal and we will most definitely take part in the race. Of course, there are a lot of Ifs still out there and we are pointing out ours here below. We are most critical to the 44 inch cabin width requirement. Our experience shows that a 40 inch cabin width is more than enough to comfortably sit 2 people for the short duration of the 200 mile course. Do consider using 40 inch cabin width in the rules. The other questions/commets are as follows:

1. Who may be the owner (only US citizens, or foreigners as well) of the competing aircraft and where can it be registered. If it has a non-US callsign and certificate, does it need to be FAA re-registered? This can cause a logistical and financial nightmare for all global Universities that would like to apply. How do they do it – directly? Through a US citizen, US company? What will be accepted? (this is under point 2.9).2. Provided that the aircraft is built and designed according to a FAA chapter, does it still need to carry a US callsign or can it be a foreign-registered aircraft?3. Further – if the aircraft to compete is not registered in the US, does is need US-issued insurance or can it be covered by insurance of the country that issued the registration docs?4. The FAA's role in this race should be better defined. When superior performance air vehicles are supposed to compete, how can a full FAA certificate be expected? This will be experimental aircraft with techologies never seen before. Why the requirement of FAA certification, FAA logbooks etc?5. Anyhow, how long is the FAA procedure to obtain the certificate for a purely experimental aircraft? For the race, does the aircraft need to fly 25 hrs after obtaining the FAA certificate or can this happen before?6. There is the mention that the sum of money not awarded in 2009 and 2010 transfers to the fund for the next year's race. What happens in 2011? Is the complete budget awarded or what happens to the "left-over" money provided no team fulfills the top-goal set for 2011?7. When a non-US University takes part in the race and wins something – how is the money awarded? The rules say that money cannot be awarded to a non-US entity.8. Under 2.6 – Financing. It says that the participant must not obtain any federal funding for the development of aircraft. Is this US federal funding or does this go for any global government funding?9. Under 5.11 – CAFE protects itself by saying that it will not award the money won if the funder fails to arrange the funds. All OK for CAFE, but does this mean that there is no real guarantee that winners will truly be awarded their money? 10. Under 1.2 – intial applications. It is written that applications are accepted until 30 Nov 2009. Do you mean 2008?

And now to the more technical questions11. For electric powered aircraft, will CAFE provide an electrical outlet to charge the systems on ground? If so, what is the voltage and what current rating can one expect from such an electrical outlet? If not, do participants bring gasolone powered field generators along?12. Can pilots be non-US citizens? There is no mention of this.13. Under 2.1 there is a mention that if more than 8 contestants apply, their acceptance will depend on the date of application and potential of success. How is will this potential be judged? There is no mention of an objective selection method, saying that one has more chances than another can be too subjective sometimes.14. Under 2.3e it says that in-flight fuel fill-ups and battery charging is not allow. What does this mean for use of Solar panels, recuperation of energy by prop-windmilling?15. Will the datasheet of the CAFE kWh meters be known in advance? Anyone who would be using electrical propulsion will wish to prepare their aircraft for fitting the CAFE kWh meter in advance. Doing the complete kWh installation to the aircraft at race-site will be difficult, maybe even dangerous because of high battery energies. Contestants should be allowed to prepare everything for a safe introduction of the kWh meter into the aircraft before the race.16. What equipement must the aircraft carry alongside COMM? Transpoder? Parachute rescue system? GPSs will probably be allowed for the race?17. Again, the 44 inch cabin should be replaced by the 40 inch rule.

We are eager to see how the 2009 rules will look like when published for real. Then we can really start to prepare ourselves for the race!

We are a very small team that is developing new aircraft and technology for the competition.

We are frustrated by the radical change of rules every year.We believe we can compete under the proposed rules, but only if they remain unchanged long enough for us to complete a project.

One other major concern is the seating configuration. If you insist on side by side Seating, we will design to that requirement. Our preference would be to allow any configuration of comfortable seating for two. Changing the requirement to 40 inches, but not allowing tandem seating would seam very arbitrary and preferential.

I think the cabin width should influence the MPGe on a weighted scale so that cabins wider than 44" will receive a MPGe credit and cabins less than 44" would have a MPGe deduction. This will allow the use of more existing airframes given the time constraints.

Forgot to add that I concur with Coandair about the need for some consistency in the rules from year to year in order to obtain meaningful advances. I would not be interested in investing the money and time for a completely one off design with the risk of the rules changing drastically the next year.

The Pitch down moment with a 3 ft chord is 113.2 ft lbs The Tail down force required at 10 feet is then 11.3 pound The required Cl of the 11.3 sq ft tail tail is 0.026 The tail drag due to lift on tail is negligable) Assumong Tail drag (both vertical & horizontal) at 20% of Wing section = 0.0012

Fuselage DragAssume fuselage has the same wetted area as the wing (150 sqft) and same Cd(Note a cylinder 4 ft in diameter and 9 ft long has a wetted area of 113 sqft area)

we add 0.0063 and 0.0012 to wing drag for fuselage and tail then calculate thrust power required

While there is little gain for configurations with low Aspect Ratio there is a 10% reduction in the thrust horsepower required for the 35 foot span design

B Use of Flaps can reduce wing area which will raise Cl in cruise and improve L/D For examples flaps could raise Cl at stall from 1.7 to up to 2.4. If these flaps extend over 1/2 the wing span, an average Cl max of 2.05 would result. This change would reduce wing area to 62 square feet ( a 17% reduction) The performance of this Design using flaps to obtain a 62 square foot wing is determined at an altitude of 4500 foot MSL

Each of these configurations require well below the 14.68 HP available at one gallon per hour fuel flow

C A more efficient airfoils could be chosen. For example the Riblett GA37-415 has a Cd of 0.0055 for Cl between o.1 to 0.6. The reduction in drag achieved might well be used in part on a increase in gross weight and therefore in the weight of Structure and Fuel

I know that this comment is late, but it pertains to a new situation. Given the current economic climate, and with it the collapse of oil prices, one would be hard pressed to design an alternate-fuel airplane to compete in the contest, as the ratios may vary throughout the design process so that e.g. an electric design may have an mpge well above 100 mpge during the process but be too low by the time the contest is run.

I propose that the mpge calculation be amended to compare the PEAK average price of each fuel over e.g. 2008. This makes sense, as, due to continuing increases in demand from China and India, oil prices will no doubt climb at least as high as they have already been as soon as our current recession is over. Prices of other fuels are less volatile.

According to the spreadsheet I just created, it should be just possible to meet the minimum mpge requirement (range, minimum speed, and even max wingspan are easy) via a Pipistrel Sinus with a reduced gross weight, shortened wings to raise the maximum L/D speed, and a probably-unavailable 50 hp, 98 lb high-efficiency (0.35 lb/hp-hr) turbo-Diesel engine.

Given $4.50/gallon gasoline and $0.09/kWh nighttime electricity (as per the chart in the rules appendix), I have also figured out how to meet the speed, range, and mpge requirements with an electric airplane using modified, very good off-the-shelf hull, propulsion system, and Li-ion modules. This is an exciting idea, but is VERY sensitive to changes in mpge ratios (it definitely will not work with gasoline at $3.50/gal). Project cost is a serious obstacle, and two areas still need innovation: meeting the 52 mph minimum speed, and reduction of wingspan to 44' for weighing. However, development money and/or sponsorships may be available, even in this economy.

Send me an email (click on my name; I made my profile public) if you are interested in possibly collaborating to field such an electric airplane entry (I'm disappointed I won't have a hope of flying it myself in the contest, as 500 hours are required and I only have 250 hours in my logbook, not all POC).

The milage rules for electric power should reflect the average efficiency of the power source. including transmission losses in the distribution system. Overall efficiency is probably not much over 40% We should check with the power companies to get a good number. This will be important as electric cars come on line.

Your car battery and the Nickel Cadmium batteries used in my 1971 designs at the birth of electric flight had an energy density of about 12 watt hours per pound. This energy density is more easily understood as 31,900 foot lbs/pound

The Perfect AirplaneA perfect airplane, that is one which has no drag, no weight, and no losses in its electric motor or propeller. This perfect airplane powered by a NiCad battery could climb to 31,900 feet. This is a lot better than rubber powered model aircraft which had flown for over 100 years. In november 1970 these simple calculations showed me electric flight was possible.

Adding real world losses next I added some real world losses to determine the top altitude for my 1971 designs.

1 first limit the electric power plant to 50% of gross weight the new altitude is 15,950 feet 2 then allocate 1/3 of the power plant weight to the motor....the new altitude is 10,633 feet3 then allocate 25% of power to electrical losses............. the new altitude is 7,975 feet4 then allocate 25% of power to propeller losses ............ the new altitude is 5,981 feet5 finally allocate 10% to aerodynamic loss (L/D = 10) ..... the new altitude is 5,383 feet

In 1980 an electric powered model sailplane demonstrated a powered climb to over 4000 feet with a similar weight allocation using commercially available Nickel Cadmium Batteries.The airplane in our example with its L/D ratio of 10:1 would have a range of about 10 miles

Designing for the Cafe Competition

Today battery performance is significantly improved and electric motors using samarium cobalt magnets weight less than their gasoline powered equivalents. Lets see how this might play out in CAFE Competition.

The lithium-ion polymer battery demonstrated by Mr Fishman in 2008 at Oshkosh has an energy density of about 72 watt hours per pound. This is six times what was available in 1971. Our Perfect Plane will start our at 191,400 feet and this time we will be a little more demanding in holding down the real life losses.

1 again limit power plant weight to 50% of gross weight - the new altitude is 95,700 feet2 next allocate 20% of power plant weight to the motor - the new altitude is 76,560 feet3 next allocate only 10% of power to electrical loss the new altitude is 68,904 feet4 next allocate only 11% of power to propeller loss -the new altitude is 61,324 feet5 finally allocate only 4% of power to aerodynamic loss -the new altitude is 58,872 feet

This paper airplane with its 24:1 Lift /Drag ratio will have a range of 268 miles. In our example the battery allocation is 40% of gross weight. The allocation could be reduced to 30% and still meet the requirements for 200 mile range. These simple calculations show that an Electric Powered Cafe competitor maw be a difficult design challenge but is certainly impossible.

1. Having in mind that personal airvehicle should have 150kts cruise at msl and 100mpg the minimal speed would be higher.2. The two place side by side is too strong limit and excludes for example 1+2+1 places layout (see my concept www.roadabletimes.com, krassin) and overall width restriction would no more than 40inches.

The CAFE Aviation Green Prize.

NASA's Centennial Challenge for aviation is operated by the non-profit CAFE Foundation in Santa Rosa, California. Prizes are funded by NASA. The CAFE Aviation Green Prize will be aviation's Centennial Challenge for 2009-2011, replacing the 2007 PAV Challenge and the 2008 GAT Challenge. For more information, click [here].